Official 30 Set 3

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Dinosaur Parenting Behavior

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What does the professor mainly discuss?
  • A. How the parenting behavior of Oviraptors may have differed from that of other dinosaurs

  • B. Evidence that parenting behavior in birds may have originated with dinosaurs

  • C. Physical traits shared by dinosaurs, crocodiles, and birds

  • D. The changing attitudes of the public toward dinosaurs

显示答案 正确答案: B

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    NARRATOR:Listen to part of a lecture in a paleontology class.

    FEMALE PROFESSOR:As we've discussed, birds are apparently descendants of dinosaurs, and share many commonalities with some dinosaur species, like, uh, feathers and maybe even flight. And of course, egg laying.

    OK, so, many paleontologists, myself included, have wondered about other similarities between dinosaurs and birds.Since adult dinosaur fossils have sometimes been discovered near, or on top of, nests, we've been looking into dinosaur parenting behavior.

    MALE STUDENT:Parenting behavior?Well, that sounds so gentle and caring. But dinosaurs were ferocious reptiles-and reptiles don't take care of their young, do they?

    FEMALE PROFESSOR:Well, some reptiles incubate their eggs-crocodiles do. And as for popular attitudes toward dinosaurs...well, take the Oviraptor for instance.

    In the 1920s, a paleontologist discovered the fossil remains of a small dinosaur near a nest containing eggs.He assumed the dinosaur was stealing the eggs, so he named it "Oviraptor."That means "egg thief" in Latin...which fueled the generally negative public image of such dinosaurs.But by the 1990s, other experts had convincingly made the case that, instead of robbing the nest, the Oviraptor was probably taking care of the eggs.

    You see, dinosaurs' closest living relatives-birds and crocodiles-display nesting behavior.And dinosaur fossils have been found in postures that we now believe to indicate brooding behavior, that is, sitting on the eggs until they hatch.So we're curious about the type of care dinosaurs gave to their young.And we'd like to figure out which dinosaur parent, the male or the female, gave the care.

    FEMALE STUDENT:Shouldn't the behavior of crocodiles and birds give us some clues, then?

    FEMALE PROFESSOR:Well, with crocodiles, it's the female who guards the nest. And with birds, it depends on the species.It can be the male or the female that takes care of the eggs. Or both. In over 90 percent of all bird species, both parents take care of the eggs... and the young birds.

    MALE STUDENT:But sometimes it's just the male?

    Well, exclusive care by the male parent is much less common, but it does occur.Now for animals other than birds, the care of young by both parents is pretty unusual in the animal kingdom-males contribute to parental care in fewer than 5 percent of all mammalian species.It's even less frequent among reptiles.And, exclusive care by the male is very rare.So, researchers have wondered about the evolution of male parenting behavior in birds for quite some time.And now there's research showing that, for some of the birds' dinosaur relatives, it's likely that the male parent was also in charge of taking care of the eggs.

    MALE STUDENT:How did they figure that out?

    FEMALE PROFESSOR:Well, first they looked at clutch volume-that's the number of eggs in the nest-of crocodiles, birds...and three types of dinosaurs, including Oviraptors, that are thought to be closely related to the dinosaur ancestors of birds.So, when researchers examined fossilized remains of nests, they found that the dinosaurs had larger clutch volumes, more eggs in the nest, that is, than most of the crocodiles and birds that were studied.But, and this is important, their clutch volumes matched those of birds that have only male parental care.You see, bird species in which only the males take care of the nest tend to have the largest clutches of eggs.

    FEMALE STUDENT:So, what's the connection between bird and dinosaur behavior?

    FEMALE PROFESSOR:Well, researchers now believe, because of this study, that the male parenting behavior of these birds might have its origins in the behavior of dinosaurs.

    FEMALE STUDENT:Based only on evidence of clutch volume size? -the number of eggs?

    FEMALE STUDENT:No, there's more.They also examined the fossilized bones of those three types of dinosaurs that were found on or near nests... to determine their sex.You see, adult female birds, during egg production, produce a layer of spongy bone tissue inside certain long bones.And so did female dinosaurs of the kinds that were investigated.This spongy tissue serves as a source of calcium for eggshell formation.But when the dinosaur fossils were examined, there were no spongy bone deposits.

    FEMALE STUDENT:Meaning that those dinosaurs on the nests were probably adult males... who wouldn't have needed calcium for making eggshells.

    FEMALE PROFESSOR:Exactly. And then there's this. Birds like the kiwi, the ostrich, and the emu-they share certain physical characteristics with these dinosaurs, and, interestingly, they also show a consistent pattern of nest care by the male.

  • 旁白:听一段古生物学课程。

    教授:正如我们讲过的,很明显,鸟类是恐龙的后代,而且鸟类与一些恐龙有很多共性,比如......羽毛甚至飞行能力。当然了,还有产卵行为。

    很多古生物学家都很好奇(包括我自己),恐龙和鸟类之间有没有别的相似之处。由于一些成年恐龙的化石有时是在恐龙巢旁或巢上发现的,我们开始研究恐龙的育儿行为。

    学生:育儿行为?听起来很温柔,充满爱意。但恐龙是非常凶残的爬行动物,爬行动物是不会照顾幼崽的,对吧?

    教授:一些爬行动物也会孵化它们的蛋,比如鳄鱼。人们对恐龙持的普遍观点......拿窃蛋龙举例吧。

    在20世纪20年代,一位古生物学家在一个有蛋的巢旁发现了一只小型恐龙的化石。他认为这只恐龙是在偷蛋,所以他将其命名为“窃蛋龙”。在拉丁语中表示偷蛋贼,这进一步恶化了这些恐龙在人们心目中的负面形象。但直到20世纪90年代,其他专家提出了令人信服的解释,认为这只窃蛋龙非但不是在洗劫这个窝巢,它很可能是在照顾这些蛋。

    恐龙最亲近的近亲——鸟类和鳄鱼——都表现出了筑巢行为。且人们也发现了一些恐龙化石,我们现在认为其化石的“姿势”显示出恐龙的孵卵行为,也就是坐在蛋上直到蛋孵化。我们很好奇,恐龙会怎样照顾它们的幼儿。我们也很想弄清楚,恐龙父母中是哪一方,雄性或雌性,来照顾幼儿的。

    学生:难道鳄鱼和鸟类的行为没给我们点提示吗?

    教授:就鳄鱼来说,是雌性鳄鱼守护窝巢,鸟类则取决于什么物种。可能是雄性或雌性来照顾自己的蛋,或双方一起。所有鸟类中,超过九成都是父母双方一同照顾鸟蛋和幼鸟。

    学生:但有时候只是雄鸟?

    仅来自父方的独有照料比较少见,但也是存在的。对于鸟类以外的动物来说,父母双方都照顾孩子在动物界很罕见的。父方会抚育孩子的物种在所有哺乳类动物中不到百分之五。这比爬行动物要少得多。仅由父方照料孩子时非常罕见的。研究者一直都很好奇,鸟类的雄性育儿行为都是怎样进化而来的。现在有研究证明,对鸟类的一些恐龙亲戚来说,很可能是父方负责照料恐龙蛋。

    学生:他们怎么发现的?

    教授:首先他们从产卵数入手,也就是鳄鱼、鸟类和三种被认为与鸟类的恐龙祖先关系非常密切的恐龙(包括窃蛋龙)窝里有多少蛋。当研究人员检验这些窝巢里的化石遗迹时,他们发现恐龙的产卵数更大,也就是说,在窝里有更多的蛋,比研究中的大多数鳄鱼和鸟类都多。但(这点很重要),它们的产卵数和鸟类中只有父方抚养幼儿的数量是吻合的。鸟类中,只有父方照顾幼儿的鸟往往有最多的蛋。

    学生:那么,鸟类和恐龙的行为之间有什么联系呢?

    教授:研究人员现在相信,由于这个研究,鸟类中的父方育儿行为可能源自恐龙行为。

    学生:证据只有产卵数吗,即蛋的数量?

    教授:还有更多证据。他们还检验了这三种在窝巢上或旁边发现的恐龙化石,来确定恐龙性别。成年的雌鸟在产卵时会在某些长骨中分泌一层海绵状的骨组织。所调查的雌恐龙中也是这样的。这层海绵组织是为蛋壳的形成提供钙质的。但人们在检验恐龙化石时,没有发现任何海绵骨沉淀。

    学生:也就是说,这些在窝里的恐龙很可能是成年雄性恐龙,它们不需要形成蛋壳所需的钙质。

    教授:正确。还有:像几维鸟、鸵鸟和鸸鹋鸟的这些鸟类,与这些恐龙有着相同的生理特征,有趣的是,它们也表现出一贯的父方育儿的模式。

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    原文定位

    OK, so, many paleontologists, myself included, have wondered about other similarities between dinosaurs and birds. Since adult dinosaur fossils have sometimes been discovered near, or on top of, nests, we've been looking into dinosaur parenting behavior.

    选项分析

    教授开篇说道鸟类是恐龙的后代,因为它们具有某些共性,后来又提到了雄性恐龙的育雏行为,并通过例子说明鸟类的育雏行为可能源于恐龙,由此可知 B 选项正确。
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